Variable-effect shotgun choke



Jan. 18, 1966 H. P. THAcKr-:R 3229,402

VARIABLE-EFFECT SHOTGUN CHOKE Filed Jan. 22, 1954 2 sheets-sheet 1 HUGH P. THACKR BY m Jan. 18, 1966 H. P. THACKER VARIABLE-EFFECT SHOTGUN CHOKE 2 Sheets-Sheet 2 Filed Jan. 22, 1964 United States Patent O 3,229,402 VARIABLE-EFFECT SHGTGUN CHOKE Hugh P. Thacker, Azusa, Calif., assigner to Horatio A. Warren, Azusa, Calif. Filed lian. 22, 1964, Ser. No. 339,411 6 Claims. (Cl. 42-79) This invention relates to an adjustably variable choke for use on shotguns.

Shotgun chokes are Well known. Their purpose is to determine the size of the shot pattern at given distances. It is not unusual for Shotguns to be provided with a plurality of chokes, but in conventional design it is necessary bodily to remove one choke and substitute it with another. This is time-consuming, and does not give the shooter a chance to change the pattern from shot to shot in normal shooting.

It is an object of this invention to provide a push button controlled choke which will selectively and adjustably change the size of the opening at the muzzle end of the barrel each time the gun is lired, and this without making any structural modilication to the gun or the choke mechanism between shots.

It is an object of this invention to provide such a mechanism which is actuated by gases developed from liring the cartridge, and to provide a simple mechanism which is rugged and substantially trouble-free.

A device according to this invention includes a collet comprising a plurality of springy fingers having cantilevered free ends disposed in a cylindrical array around a central axis at the muzzle of the gun. A shotgun load is lired axially through this array, the free ends determining the shot pattern by forming the choke. A plurality of contact regions disposed at dilierent radial distances from the axis is disposed on the outside of each of said lingers. These contact regions are disposed at different axial locations along the lingers. An axially movable shroud embraces the periphery of these spring lingers and is adapted to contact the contact regions, whereby to flex the free ends toward and away from said axis to vary their spacing-apart. Gas actuated means is provided for shifting the shroud, and selectible, actuable limit Vstop means is provided for stopping the shroud at a selected position in opposition to the gas actuated means.

According to a preferred but optional feature of this invention, the limit stop means comprises a plurality of substantially equally-spaced apart push buttons. This arrangement is most convenient for the shooters hand. These buttons are respectively operable on ones of a plurality of differentially spaced stops. These stops are, when pressed, adapted t-o engage the gas-actuated means and stop the latter means at a selected point, thereby determining the axial position to be assumed by the shroud, and the radial locations ofthe lingers.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings in Iwhich:

FIG. l is a bottom view partly in cutaway cross-section of a shotgun stock incorporating the invention;

FIG. 2 is a side elevation partly in cutaway cross-section taken substantially at line 2 2 of FIG. l;

FIG. 3 is a side elevation partly in cutaway cross-section of the muzzle end of a shotgun utilizing the invention, the left-hand end of FIG. 3 registering with the right-hand end of FIG. 2; and

FIG. 4 is a right-hand end view of FIG. 3 taken at line 4 4 thereof.

FIGS. 1 and 2 show the general orientation of the invention wherein a shotgun barrel 1li carries adjacent to it a typical stock 1i. Other conventional elements such as a shoulder rest, trigger assembly and the like, are not 3,229,402 Patented Jani. 18, 1966 shown, because they are not pertinent to an understanding of the instant invention.

The barrel includes a -shell chamber 12 adapted to receive the shotgun shell with its powder load and its shot. The objective is to discharge the shot in a pattern of selected size through the barrel to the right in FIGS. l3, inclusive, the size of the pattern being varied accord ing to the shooters choice for each shell which is discharged by pressing a selected push button. The mechanical adjustment is then accomplished automatically by gas pressure in the barrel that is developed by the charge. In FIGS. 1 3, the same barrel is shown. The scale is not the same between FIGS. l, 2 and 3, FIG. 3 being enlarged for convenience in disclosure.

The right-hand end of the barrel in FIG. 3 is the muzzle end, and the left-hand end of the barrel in FIGS. 1 and 2 is the loading end.

As is conventional in shotgun practice, the choke is located at the muzzle end. In this invention, the barrel itself is divided into a plurality of spring lingers 13-18, inclusive, by slits 319-24, inclusive. Each of fingers 13-18 has a free end 25-30, respectively, these free ends and the respective ling-ers being formed around central axis 31 in a circumferential, cylindrical array, Crack-stopping holes 32 are drilled at the base ends of the slits. It will be understood that in this embodiment, the material of the barrel itself is slit into lingers to form a collet. Alternatively, a barrel extension of the same construction could be attached to the barrel itself, thereby accomplishing the objectives of the invention without requiring modification of the barrel.

The springy fingers have outside surfaces which include contact regions. These contact regions are spaced-apart axially, and each finger has a portion thereof. Finger i6 is shown in detail, and is typical lof all. It carries contact regions 33, 34, 35 and 36. These are disposed at different radial distances from the central axis so that when contacter 37 on the inside of a shroud 38 contacts the regions the free ends of the lingers are variably an-d adjustably shifted toward and away from the central axis, the lingers being initially sprung outwardly so as to be biased against the shroud at all positions thereof. The shroud is a continuous tube, and contactor 37 is a continuous peripheral shoulder within the contacter. The assembly comprises a simple collet `of a type Well known in the machine tool art.

A push rod 39 serves to move the shr-oud axially, the shroud making an embracing fit with a substantial portion 4t) of the outside of the barrel for guidance and radial support. It will now be seen that axial motion of the push rod will cause the free ends of the collet (choke) to be opened and closed depending on the relationship between the contactor and the various contact regions.

Now with reference to FIGS. l and 2 it will be seen that the push rod 39 appears at the right-hand end of these figures and it is tied through a screw 41, rivet, or other connecting means, to a piston 42. This piston forms a gas-actuated means 43 which serves to shift the shroud axially.

A barrel-tapping port 45 is drilled through the side of the barrel downstream of the shell where it will receive gas pressure derived from the deliagration of the charge which lires the shot out of the barrel. This port fluidly interconnects the barrel at this region to a cylinder 44 within which a piston head 46 fits in fluid-sealing relationship. A plug 47 closes the left-hand end of the cylinder, and a spring 48 biases the head toward the left-hand end.

A stop 49 engages the right-hand end of spring 48. The piston includes a rod 50 with four engagement shoulders 5l, 52, 53, 54. These shoulders may be turned from a cylindrical metal piece, along with the piston head.

ICC

Four grooves, 55, 56, 57, 58 are formed adjacent to the engagement shoulders. A plurality of stops 59, 61B, 61, 62 is provided, of which stops 59, 60 and 61 are radially shiftable relative to the piston rod, and stop 62 is a permanent stop which is threaded into the wall of the cylinder. Bias springs 63, 64, `65 are provided to bias stops 59, 60, 61, respectively, out of the path of the engagement shoulders.

A keeper plate 66 is threaded to the stock within a cavity 67 therein, adjacent to three push button cavities 68, 69, 70. Each cavity receives a respective push button 71, 72, 73. These push buttons are biased outwardly by springs 74, 75, 76. It will now be seen that four adjustments of the choke are attainable, one where no push button is actuated, and three others where individual ones of the push buttons are actuated. The stems 77, 78, 79 of push buttons 71, 72, 73 are operable to press on respective stops 59, 60 and 61 to move them into the path of shoulders 51, 52 and 53.

The operation of this device will now be described. Because the generation of gas to tire the shot is quite sudden, and because the shot takes an appreciable time to travel the length of the barrel, gas introduced into the cylinder through the barrel-tapping port 45 attains a suiiicient pressure to overcome spring 48, move the piston, push rod and shroud, and thereby set the collet before the shot arrives there. The mass of the parts moved by gas pressure is kept as small as possible to reduce the reaction time of the system.

When the charge is fired, gas under pressure enters port 45 and against the force of spring 48 forces the piston to the right. If none of the push buttons is pushed down, there will be no impediment to the motion of the piston to the rigth until shoulder 54 strikes stop 62. The piston will then have travelled the dimension labelled C in FIGURES 1 and 3, which distances are equal unless multiplied by some multiplying linkage. This will place the contactor 37 on regions 36 and contract the free ends of the springy fingers to some setting.

Were a different setting to be desired, push button 70 could have been pressed, in which case the gas would have caused the piston to move to the right in FIG. 1 until shoulder 53 strikes stop 61, because this is the stop which would be shifted by the push button. This would require the movement of the piston, push rod and shroud shown as dimension B, which is equal in FIGS. 1 and 3, unless a multiplying linkage is used, thereby placing the contactor 37 on contact region 3S and placing the free ends of .the springy lingers at another radial position.

Should still another pattern have been desired, then push button 72 could have been pressed. Stop 60 would then have been placed in the path of shoulder 52 and the piston would have moved through dimension A in FIGS. 1 and 3, causing contactor 37 to contact region 34 and move the lingers to still another setting.

FIGS. 1, 2 and 3 show the device in its rest condition with the bias spring having moved the piston to the left and contactor 37 in contact region 33. Were this setting to be retained, then push button 71 would be pressed down placing stop 59 in the path of shoulder 51, preventing any motion whatever of the piston, thereby keeping contactor 37 in contact with region 33 for still another choke setting.

After the shot leaves the barrel, the gas Will bleed out of the cylinder into the barrel, and spring 48 will move the piston to the left, returning the shroud to the position shown in FIG. 4.

The arrangement shown in FIG. 1 is especially suitable because it permits the buttons to be equidistantly spaced which is most convenient for use with the fingers. However, it will be understood that there are other readilydevised arrangements whereby the length of travel of the piston can be selectively stopped each round, this simply being the presently preferred embodiment.

. This invention thereby provides a means whereby the pattern of shot can be varied for each round fired at the time it is fired requiring no removal and replacement, or adjustment of the basic shotgun, shell, or choke construction.

This invention is not to be limited by the embodiments shown in the drawings and described in the description which are given by Way of example and not of limitation, but only in accordance with the scope of the appended claims.

I claim:

1. A variable-effect shotgun choke adapted to be used in combination with a shotgun barrel and a source of fluid pressure derived therefrom, comprising: a `collet comprising a plurality of springy fingers having cantilevered free ends disposed in a cylindrical array around a central axis through which array a shot is to be fired axially, the spacing apart of the free ends determining its pattern; a plurality of contact regions disposed on the outside of each of said fingers at different radial distances from the axis and spaced apart along the axis; an axially-shiftable shroud embracing the periphery of said spring fingers and contacting the contact regions, whereby to flex the lingers toward and away from said axis as a function of its axial position to vary the spacing apart of the free ends of the lingers and thereby the cross-sectional area between them; gas-actuated means for shifting said shroud comprising a cylinder adapted to be liuidly connected to the shotgun barrel, and a piston in slidable, fluid-sealing relationshiip with the wall of the cylinder; and limit-stop means for stopping said shroud at selected positions in opposition to said gas-actuated means comprising a plurality of means to stop the pistons motion at different points along its travel, at least one of said last-named means being a movable stop selectively movable into the path of the piston, .and another of which is a permanent stop.

2. A variable-effect shotgun choke adapted to be used in combination with a shot gun barrel and a source of fluid pressure derived therefrom, comprising: a collet comprising a plurality of springy fingers having cantilevered free ends disposed in a cylindrical array around a central axis through which array a shot is to be tired axially, the spacing apart of the free ends determining its pattern; a plurality of contact regions disposed on the outside of each of said fingers at different radial distances from the axis and spaced apart along the axis; an axiallyshiftable shroud embracing the periphery of said spring fingers and contacting the contact regions, whereby to ex the lingers toward and away from said axis as a function of its axial position to vary the spacing apart of the free ends off the fingers and thereby the cross-sectional area between them; gas-actuated means for shifting said shroud comprising a cylinder adapted to be fluidly connected to the shotgun barrel, and a piston in slidable, fluidsealing relationship with the wall of the cylinder; and limit-stop means for stopping said shroud at selected positions in opposition to said gas-actuated means comprising a plurality of means to stop the pistons motion at dilerent points along its travel, said last-named means comprising a plurality of differentially-spaced shoulders on the piston, a plurality of substantially equally-spaced push buttons, and a plurality of movable stops selectively movable by the push .buttons into the path of a respective shoulder thereby to stop the piston at a point of its travel determined by the selected limit-stop means.

3. In combination, a shotgun including a barrel with a central axis, and a stock, and a variable-effect shotgun choke, said choke comprising: a collet carried by the barrel comprising a plurality of springy lingers having cantilevered free ends disposed in a cylindrical array around the central axis through which array a shot is to be fired axially, the spacing apart of the free ends determining its pattern; a plurality of contact lregions disposed on the outside of each of said lingers at ditferent radial distances from the axis and spaced apart along the axis; an axially-shiftable shroud embracing the periphery of said spring nrgers and contacting the contact regions, whereby to flex the ngers toward and away from said axis as a function of its axial position to vary the spacing apart of the free ends of the fingers and thereby the crosssectional area between the-m; gas-actuated means for shifting said shroud comprising a cylinder adapted to be uidly connected to the shotgun barrel, and a piston in slidable, fluid-sealing relationship with the wall of the cylinder; and limit-stop means for stopping said shroud at selected positions in opposition to said gas-actuated means comprising a plurality of means to stop the pistons motion at different points along its travel, at least one of said last-named means being a movable stop selectively movable tinto the path of the piston, and another of which is a permanent stop.

4. In combination, a shotgun including a barrel with a central axis, and a stock, and a variable-effect shotgun choke, said choke comprising: a collet carried by the barrel comprising a plurality of springy fingers having cantilevered -free ends disposed in a cylindrical array around lthe central axis through which array a shot is to be fired axially, the spacing apart of the free ends determining its pattern; a plurality of contact regions disposed 0n the outside of each of said lingers at different radial distances 'from the axis and spaced apart along the axis; an axially shiftable shroud embracing the periphery of said spring lingers and contacting the contact regions, whereby to Hex the fingers toward and away from said axis as a function of its axial position to vary the spacing apart of the free ends of the ngers and thereby the crosssectional area between them; gas-actuated means ttor shifting said shroud comprising a cylinder adapted to be uidly connected to the shotgun barrel, and a piston in slidable, fluid-sealing relationship with the wall of the cylinder; and limit-stop means for stopping said shroud at selected positions in opposition to said gas-actuated means comprising a plurality of means to stop the pistons motion at different points along its travel, said lastnamed means comprising a plurality of differentiallyspaced shoulders on the piston, a plurality of substantially equally-spaced pus-h buttons, and a plurality of movable stops selectively movable by the push buttons into the path of a respective shoulder thereby to stop the piston at a point of its travel determined by the selected limit-stop means.

5. A combination according to claim 4 in which the push buttons are disposed in the stock, and in which a push rod interconnects the piston and the shroud.

6. A combination according to claim 5 in which a return spring opposes motion of the piston caused by fluid pressure exerted on said piston.

References Cited by the Examiner UNITED STATES PATENTS 2,765,564 10/1956 Schroeder a 42-79 2,779,119 1/ 1957 Fawcett 42--79 2,856,719 10/ 1958 Metz 42-79 2,867,932 1/ 1959 Keightley 42--79 2,922,242 1/ 1960 Pachmayr et al 42-79 BENJAMIN A. BORCHELT, Primary Examiner. 

1. A VARIABLE-EFFECT SHOTGUN CHOKE ADAPTED TO BE USE IN COMBINATION WITH A SHOTGUN BARREL AND A SOURCE OF FLUID PRESSURE DERIVED THEREFROM, COMPRISING: A COLLET COMPRISING A PLURALITY OF SPRINGY FINGERS HAVING CONTILEVERED FREE ENDS DISPOSED IN A CYLINDRICAL ARRAY AROUND A CENTRAL AXIS THROUGH WHICH ARRAY A SHOT IS TO BE FIRED AXIALLY, THE SPACING APART OF THE FREE ENDS DETERMINING ITS PATTERN; A PLURALITY OF CONTACT REGIONS DISPOSED ON THE OUTSIDE OF EACH OF SAID FINGERS AT DIFFERENT RADIAL DISTANCES FROM THE AXIS AND SPACED APART ALONG THE AXIS; AN AXIALLY-SHIFTABLE SHROUD EMBRACING THE PERIPHERY OF SAID SPRING FINGERS AND CONTACTING THE CONTACT REGIONS, WHEREBY TO FLEX THE FINGERS TOWARD AND AWAY FROM SAID AXIS AN A FUNCTION OF ITS AXIAL POSITION TO VARY THE SPACING APART OF THE FREE ENDS OF THE FINGERS AND THEREBY THE CROSS-SECTIONAL AREA BETWEEN THEM; GAS-ACTUATED MEANS FOR SHIFING SAID SHROUD COMPRISING A CYLINDER ADAPTED TO BE FLUIDLY CONNECTED TO THE SHOTGUN BARREL, AND A PISTON IN SLIDABLE, FLUID-SEALING RELATIONSHIP WITH THE WALL OF THE CYLINDER; AND LIMIT-STOP MEANS FOR STOPPING SAID SHROUD AT SELECTED POSITIONS IN OPPOSITION TO SAID GAS-ACTUATED MEANS COMPRISING A PLURALITY OF MEANS TO STOP THE PISTON''S MOTION AT DIFFERENT POINTS ALONG ITS TRAVEL, AT LEAST ONE OF SAID LAST-NAMED MEANS BEING A MOVABLE STOP SELECTIVELY MOVABLE INTO THE PATH OF THE PISTON, AND ANOTHER OF WHICH IS A PERMANENT STOP. 